Use of aluminum to save weight in internal combustion engines has now become an accepted solution and a concentrated area of development. Other lightweight materials will also become of importance and will require similar development. However, there are noticeable problems to be overcome by the engine designer when incorporating these materials into parts of the engine subjected to both wear and a severe corrosive atmosphere. It had been hoped that by the introduction of aluminum alloys containing high silicon, resistance to wear would be overcome. But in certain applications, wear surfaces experience periods where normal engine lubrication is at a minimum and, in fact, the oil film may be washed off of such wear surfaces during the cold-start engine condition. Accordingly, at these areas, particularly where the skirt of a piston meets with the bore surface, the material is not able to cope with such condition without wearing excessively.
A variety of solutions have been undertaken by the prior art to remedy this, one of which is to apply a variety of coatings to the aluminum substrate, among which include zinc, copper, hard iron, or an electroplated tin second coating. The obvious disadvantages of these coatings are their expense and low rate of productivity. Another approach has been to immerse the aluminum parts in an aqueous solution of tin or lead, the tin or lead coating all or a major portion of the part that has been so immersed. The unfortunate result of this technique is that the portion of the part so coated is far in excess of the local area or zone requiring such treatment and thus is expensive and wasteful.